The tetracycline operon system, comprising repressor and operator elements, was originally isolated from bacteria. The operon system is tightly controlled by the presence of tetracycline, and self-regulates the level of expression of tetA and tetR genes. The product of tetA removes tetracycline from the cell. The product of tetR is the repressor protein that binds to the operator elements with a Kd of about 10 pM in the absence of tetracycline, thereby blocking expression or tetA and tetR.
This system has been modified to control expression of other polynucleotides of interest, and/or for use in other organisms, mainly for use in animal systems. Tet operon based systems have had limited use in plants, at least partially due to problems with the inducers which are typically antibiotic compounds, and sensitive to light.
There is a need to regulate expression of sequences of interest in organisms, compositions and methods to tightly regulate expression in response to sulfonylurea compounds are provided.